Chin Paul C, Majdzadeh Nazanin, D'Mello Santosh R
Department of Molecular and Cell Biology, University of Texas at Dallas, 2601 N. Floyd Road, Richardson, TX 75083, USA.
Brain Res Mol Brain Res. 2005 Jun 13;137(1-2):193-201. doi: 10.1016/j.molbrainres.2005.03.004. Epub 2005 Apr 26.
Depolarizing concentrations of potassium (HK, 25 mM), cyclic AMP elevating agents and analogs (cAMP), insulin-like growth factor-1 (IGF-1), or lithium can maintain the survival of cultured rat cerebellar granule neurons (CGNs). We investigated the possibility that the signal transduction pathways utilized by these four survival factors converge in regulating a common molecular target. We targeted the regulation of the kinase GSK3beta as the critical event in the survival directed by the four survival factors. We found that treatment of CGNs with HK, the cAMP-elevating agent forskolin, IGF-1, and lithium resulted in phosphorylation of GSK3beta at serine-9 and thus its inactivation. Furthermore, pharmacological inhibition of core components in the survival signaling cascades initiated by HK, forskolin, IGF-1, and lithium causes apoptosis and activation of GSK3beta accompanies this death. Finally, we examined the pharmacological inhibitors of GSK3beta, GSK3 inhibitor I, TDZD-8, and SB-415286, for their ability to prevent low potassium (LK)-induced apoptosis. Although previous reports demonstrate inhibition of GSK3beta in in vitro kinase assays with GSK3 inhibitor I and TDZD-8, we were unable to detect inhibition of GSK3beta in neuronal cultures treated with these compounds and thus no protection from LK-induced apoptosis. SB-415286 on the other hand, was able to rescue CGNs from cell death. Taken together, we conclude that regulation of GSK3beta is a critical convergence event in the promotion of CGN survival by different factors.
去极化浓度的钾（HK，25 mM）、环磷酸腺苷升高剂及其类似物（cAMP）、胰岛素样生长因子-1（IGF-1）或锂可维持培养的大鼠小脑颗粒神经元（CGN）的存活。我们研究了这四种存活因子所利用的信号转导途径在调节共同分子靶点方面是否存在汇聚的可能性。我们将糖原合成酶激酶3β（GSK3β）的调节作为这四种存活因子介导存活的关键事件。我们发现，用HK、环磷酸腺苷升高剂福斯高林、IGF-1和锂处理CGN会导致GSK3β的丝氨酸9位点磷酸化，从而使其失活。此外，对HK、福斯高林、IGF-1和锂引发的存活信号级联反应中的核心成分进行药理学抑制会导致细胞凋亡，并且GSK3β的激活伴随着这种死亡。最后，我们检测了GSK3β的药理学抑制剂GSK3抑制剂I、TDZD-8和SB-415286预防低钾（LK）诱导的细胞凋亡的能力。尽管先前的报告表明在体外激酶试验中GSK3抑制剂I和TDZD-8可抑制GSK3β，但我们在使用这些化合物处理的神经元培养物中未能检测到GSK3β受到抑制，因此它们无法保护细胞免受LK诱导的细胞凋亡。另一方面，SB-415286能够挽救CGN免于细胞死亡。综上所述，我们得出结论，GSK3β的调节是不同因素促进CGN存活的关键汇聚事件。
